In the present study, a commercial TiO₂, several BiVO₄ photocatalysts, a WO₃ nanomaterial, and their composites were used to prepare photocatalytic polyvinylidene fluoride (PVDF) ultrafilter membranes. Their photocatalytic activities and the effects of coatings on the filtration of oil‐in‐water emulsion (crude oil; c_oil = 100 mg L⁻¹) were investigated. Fluxes, filtration resistances, purification efficiencies, and fouling resistance abilities—like flux decay ratios (FDRs) and flux recovery ratios (FRRs)—were compared. The solar light‐induced photocatalytic decomposition of the foulants was also investigated. WO₃ was used as a composite component to suppress the electron–hole recombination with the goal of achieving higher photocatalytic activity, but the presence of WO₃ was not beneficial concerning the filtration properties. However, the application of TiO₂, one of the investigated BiVO₄ photocatalysts, and their composites was also beneficial. In the case of the neat membrane, only 87 L m⁻² h⁻¹ flux was measured, whereas with the most beneficial BiVO₄ coating, 464 L m⁻² h⁻¹ flux was achieved. Pure BiVO₄ coating was more beneficial in terms of filtration properties, whereas pure TiO₂ coating proved to be more beneficial concerning the photocatalytic regeneration of the membrane. The TiO₂(80%)/BiVO₄(20%) composite was estimated to be the most beneficial combination taking into account both the aspects of photocatalytic activity and filtration properties.

Non-solvent induced phase-inversion is one of the most used methods to fabricate membranes. However, there are only a few studies supported by statistical analysis on how the different fabrication conditions affect the formation and performance of membranes. In this paper, a central composite design was employed to analyze how different fabrication conditions affect the pure water flux, pore size, and photocatalytic activity of polyvinylidene fluoride (PVDF) membranes. Polyvinylpyrrolidone (PVP) was used to form pores, and titanium dioxide (TiO₂) to ensure the photocatalytic activity of the membranes. The studied bath temperatures (15 to 25 °C) and evaporation times (0 to 60 s) did not significantly affect the pore size and pure water flux of the membranes. The concentration of PVDF (12.5 to 17.5%) affected the viscosity, formation capability, and pore sizes. PVDF at high concentrations resulted in membranes with small pore sizes. PVP affected the pore size and should be used to a limited extent to avoid possible hole formation. TiO₂ contents were responsible for the decolorization of a methyl orange solution (10⁻⁵ M) up to 90% over the period studied (30 h). A higher content of TiO₂ did not increase the decolorization rate. Acidic conditions increased the photocatalytic activity of the TiO₂-membranes.

This comparative study investigates the modification of polyvinylidene fluoride (PVDF) membranes with different nanoparticles (TiO₂ or TiO₂-based composites containing BiVO₄ and/or CNT), using three distinct methods (blending, coating, and grafting) and polyvinylpyrrolidone (PVP). The objective was to enhance the photocatalytic and filtration performance for the separation of oil-in-water emulsions. Regarding the UV activity, the PVDF-TiO₂/CNT/PVP-coated membrane presented the best performance. Overall, the addition of 2 wt.% CNT to the TiO₂ notably enhanced the photocatalytic activity of the membranes for both UV and visible irradiations. Meanwhile, the presence of 2 wt.% BiVO₄ was beneficial only for photocatalysis under visible light irradiation. Regarding the filtration of the oil-in-water emulsions, 2 wt.% CNT or BiVO₄ addition resulted in the highest fluxes in the series of the PVDF-TiO₂-grafted membranes. The presence of pore former PVP led to relatively high fluxes and photocatalytic activities for all series. Regarding the modification methods, coated membranes showed the highest photocatalytic efficiency and lowest fluxes. Grafted membranes showed relatively high photocatalytic efficiencies and the best filtration performances.

This study demonstrated a complex research about the development of composite nanomaterial-modified, photocatalytically active membranes used for the treatment of oily wastewater. It presents a deep review of oily wastewaters, highlighting the advantages and the barriers of membrane filtration in the treatment of oily wastewaters. It was presented how membrane modification appears as an important step to avoid fouling and flux reduction which are still the major limitation to the application of these technologies. The modification methods by adding nanomaterials were also explained: blending, coating, and grafting methods. In addition, it was demonstrated how super hydrophilic photocatalytic membranes are promising for the treatment of oil-contaminated waters because of their simultaneous efficiency in both degrading and separating organic pollutants from the feedwater, resulting in membranes with self-cleaning properties and good anti-fouling properties. The review showed the limitations of TiO2 and presented other photocatalytic composite nanomaterials that can be activated with high efficiency by UV or even by visible/solar light, demonstrating huge potential to (i). enhance membrane performance and antifouling properties, (ii). be cost-effective, (iii). enable chemical-free membrane cleaning, iv. improve the degradation of pollutants, possibly by the utilization of a cost-free light source – the Sun. A key aspect of this research is the enhancement of membrane performance through the application of photocatalytic nanomaterials. TiO2, BiVO4, and CNT in composites with PVP pore former addition were employed to improve the filtration efficiency, fouling resistance, and photocatalytic activity of PVDF membranes. The research aimed to synthesize BiVO4 photocatalyst and evaluate its addition onto membrane surfaces, evaluating filtration performance and recoverability. In addition, it aimed to investigate the effects of various membrane fabrication conditions on membrane properties and performances to develop phase-inversion made PVDF membranes with desired properties. The effects of experimental conditions were analyzed by CCD statistical analysis. After this, the addition of CNT and/or BiVO4 to the TiO2-PVDF and TiO2-PVP/PVDF membranes was also evaluated considering their photocatalytic efficiencies and filtration performance using three different modification methods (blending, coating, and grafting). Overall, this research underscores the potential of PVDF membranes enhanced with photocatalytic nanoparticles for efficient oily wastewater treatment. The exploration of different coating materials, fabrication conditions, and modification methods drives avenues for optimizing membrane performance in terms of filtration efficiency, fouling resistance, and photocatalytic activity.